U.S. patent number 7,491,946 [Application Number 11/346,666] was granted by the patent office on 2009-02-17 for electrostatic deflection system for corpuscular radiation.
This patent grant is currently assigned to Leica Microsystems Lithography GmbH. Invention is credited to Christoph Damm, Hans-Joachim Doering, Thomas Elster, Andreas Gebhardt, Thomas Peschel, Stefan Risse, Mathias Rohde, Christoph Schenk, Gerhard Schubert.
United States Patent |
7,491,946 |
Risse , et al. |
February 17, 2009 |
Electrostatic deflection system for corpuscular radiation
Abstract
The invention is directed to electrostatic deflection systems
for corpuscular beams which can be used particularly in
microstructured and nanostructured applications in lithography
installations or measuring equipment. According to the proposed
object of the invention, the individual electrodes of a deflection
system of this kind should permanently have and retain a very exact
axially symmetric arrangement relative to one another. In the
electrostatic deflection system according to the invention,
rod-shaped electrodes are held in an axially symmetric arrangement
in an inwardly hollow carrier through which a corpuscular beam can
be directed. The carrier is formed of at least two, and at most
four, carrier members which are connected to one another.
Inventors: |
Risse; Stefan (Jena,
DE), Peschel; Thomas (Jena, DE), Damm;
Christoph (Jena, DE), Gebhardt; Andreas (Apolda,
DE), Rohde; Mathias (Jena, DE), Schenk;
Christoph (Jena, DE), Elster; Thomas (Jena,
DE), Doering; Hans-Joachim (Jena, DE),
Schubert; Gerhard (Jena, DE) |
Assignee: |
Leica Microsystems Lithography
GmbH (Jena, DE)
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Family
ID: |
36580030 |
Appl.
No.: |
11/346,666 |
Filed: |
February 3, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060192133 A1 |
Aug 31, 2006 |
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Foreign Application Priority Data
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Feb 4, 2005 [DE] |
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10 2005 005 801 |
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Current U.S.
Class: |
250/396R |
Current CPC
Class: |
G21K
1/087 (20130101) |
Current International
Class: |
H01J
37/147 (20060101) |
Field of
Search: |
;250/396R,492.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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31 38 898 |
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Apr 1983 |
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DE |
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199 30 234 |
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Dec 1999 |
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DE |
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0 999 572 |
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May 2000 |
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EP |
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1 033 738 |
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Sep 2000 |
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EP |
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57-206172 |
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Dec 1982 |
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JP |
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59-180943 |
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Oct 1984 |
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JP |
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2-247966 |
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Oct 1990 |
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JP |
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5-129193 |
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May 1993 |
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JP |
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Primary Examiner: Nguyen; Kiet T
Attorney, Agent or Firm: Reed Smith LLP
Claims
What is claimed is:
1. An electrostatic deflection system for corpuscular beams,
comprising: an axially symmetric arrangement through which an
electron beam is directed, said arrangement being formed as an
inwardly hollow carrier in which rod-shaped electrodes are held;
said carrier having two ends in direction of a longitudinal
symmetry axis of the deflection system and being formed of at least
two carrier members which are connected to one another.
2. The deflection system according to claim 1, wherein said carrier
members are provided with first and second support areas for the
electrodes and the electrodes are fixed to the first and second
support areas by material bonding.
3. The deflection system according to claim 2, wherein the first
and second support areas are formed at ends of the carrier
members.
4. The deflection system according to claim 3, wherein the first
and second support areas are constructed in a stair-shaped manner
and the electrodes are each arranged to rest in a groove of a step
of the stair-shaped support areas in an axially symmetric
arrangement.
5. The deflection system according to claim 4, wherein the grooves
of the steps form a 90-degree V-groove.
6. The deflection system according to claim 2, wherein at least one
additional support area is formed between the first and second
support areas arranged at ends of the carrier members.
7. The deflection system according to claim 2, wherein the carrier
members and the electrodes are both formed of a dielectric
material, and the carrier members are provided with an interior
electrically conductive coating, and the electrodes are provided an
exterior electrically conductive coating.
8. The deflection system according to claim 2, wherein the
electrodes are connected to the carrier members at the support
areas by material bonding so as to be electrically insulated.
9. The deflection system according to claim 2, wherein shielding
flanges are arranged near the support areas.
10. The deflection system according to claim 1, wherein electrodes
that have a curvature are so oriented in the carrier members that a
convex curvature is directed radially outward in relation to the
longitudinal symmetry axis of the deflection system.
11. The deflection system according to claim 10, wherein the
electrodes are ground at an oblique angle on at least one end
face.
12. The deflection system according to claim 10, wherein a mark
indicating the orientation of the curvature of the electrodes is
provided at the electrode.
13. The deflection system according to claim 1, wherein the
electrodes are arranged on at least two different diameters in
relation to the longitudinal symmetry axis of the deflection
system.
14. The deflection system according to claim 1, wherein the
electrodes are held in the carrier members at different
diameters.
15. The deflection system according to claim 1, wherein two
shielding flanges form outer terminations at ends of the carrier
members and are connected by material bonding to the carrier
members that have been connected to one another.
16. The deflection system according to claim 15, wherein electrical
contact for the individual electrodes is integrated in or on one of
the shielding flanges or arranged at the shielding flanges.
17. The deflection system according to claim 1, wherein the
electrodes are produced from glass by a drawing process.
18. The deflection system according to claim 1, wherein an
electrically conductive coating of the electrodes is formed of a
layer system comprising a plurality of layers of different metals
which are formed one above the other.
19. The deflection system according to claim 18, wherein the layer
system is formed of titanium, platinum and gold.
20. The deflection system according to claim 1, wherein the carrier
members are formed of glass ceramic and have an interior
electrically conductive coating comprising a nickel layer on which
a layer of gold is formed.
21. The deflection system according to claim 20, wherein regions on
which there is no electrically conductive coating are provided at
support areas for the electrodes so that the electrodes can be
fastened to the carrier members so as to be electrically insulated.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of German Application No. 10 2005
005 801.9, filed Feb. 4, 2005, the complete disclosure of which is
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to electrostatic deflection systems for
corpuscular radiation which can be used particularly for
microstructured and nanostructured applications in lithography
installations or measuring equipment (e.g., REM).
b) Description of the Related Art
For processes such as those mentioned above, it is desirable to
have the capability for high-precision deflection of charged
corpuscles, particularly electrons with a small time constant.
Further, a deflection system of this type should have only a small
space requirement so that it can be installed in favorable
positions in the electron-optical installation.
DE 199 30 234 A1 discloses an electrostatic deflection device in
which the rod-shaped electrode elements are arranged inside a
holding device The individual electrode elements are produced from
a conductive ceramic material with a predetermined specific
resistance. The holding device is constructed as a hollow
cylindrical tube. The individual electrode elements are then
inserted into the holding device in a desired axially symmetric
arrangement and are connected to the holding device by material
bonding.
In this connection, it has turned out that the adjustment accuracy
required for a high-precision deflection of a corpuscular beam when
the individual electrode elements are arranged relative to one
another so as to maintain exact axial symmetry cannot be met during
assembly on the one hand and, on the other hand, connection by
material bonding leads to deviations in the positioning of the
individual electrode elements at the holding device. The
material-bonding connection is produced by spot-soldered or glued
connections through openings formed in the holder.
Deflection systems should also be suitable for use in rapidly
changing magnetic fields, which is advantageous for low-aberration
electron-optical solutions.
Deflection devices for electron beams which are not easily
reproducible can also be produced in this form.
Further, deflection systems in which the individual electrodes are
formed of tensioned wires are also known as is described, for
example, in EP 1 033 738 A1. The wires, to which tensile force is
applied, form weak points particularly in that they are exposed to
high mechanical loads at their material-bonded connection points
which can result in detachment or in different pretensioning.
Further, the wires forming individual electrodes can have
deviations in electrical parameters which lead to inhomogeneity in
the electrical fields that can be used for the deflection of
electron beams.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, it is the primary object of the invention to provide an
electrostatic deflection system for corpuscular radiation in which
the individual electrodes permanently have and retain a very exact
axially symmetric arrangement relative to one another.
According to the invention, this object is met by an electrostatic
deflection system for corpuscular radiation comprising an axially
symmetric arrangement in which electrodes are held in an inwardly
hollow carrier through which an electron beam is directed. The
carrier is formed of at least two, and at most four, carrier
members which are connected to one another.
The electrostatic deflection system according to the invention
likewise uses a plurality of rod-shaped electrodes, as is known
from the prior art, which are held in an axially symmetric
arrangement in an inwardly hollow carrier. The respective
corpuscular radiation to be deflected can then be directed through
this hollow carrier so that its deflection can be influenced for
lithographic applications by the electrical fields which are formed
around the rod-shaped electrodes and which can be influenced in a
corresponding manner. The carrier according to the invention is
formed of at least two, and at most four, carrier members which are
connected to one another. The carrier is preferably formed by two
carrier members.
The individual carrier members can be fitted with the rod-shaped
electrodes prior to the actual assembly of the carrier members to
form an individual carrier. In this way, there is very good access
to the interior of the carrier when inserting the rod-shaped
electrodes in an advantageous arrangement so that it is possible to
exactly position and adjust the rod-shaped electrodes and to fix
the electrodes to the carrier members beforehand. This also
facilitates access for optical or tactile measurement methods.
The carrier members forming the carrier can preferably be
mechanically machined beforehand so that they can be precisely
positioned, adjusted and subsequently connected to one another,
preferably by material bonding, when assembling a carrier. During
assembly, the arrangement of the individual electrodes is retained
and the axial symmetry is produced for the entire system.
It is advantageous for the positioning and adjustment of the
rod-shaped electrodes to provide support areas for the electrodes
at the carrier members. The individual electrodes can then be fixed
to the respective support areas by material bonding. This can
preferably be carried out by means of solder connections but also
by glue connections.
The individual electrodes should have already been supported and
fixed at two support areas at a distance from one another.
In a particularly advantageous manner, the support areas are formed
at the ends directly on the carrier members. The support areas can
be formed at annular flanges formed in the interior of a carrier
formed of carrier members. One support area should be formed at the
end face of the carrier member and another support area should be
formed at the opposite end face of the carrier member.
The support areas can preferably be constructed in a stair-shaped
manner which can be carried out in a highly precise manner by
mechanical machining at the respective carrier members.
For an exact positioning of the electrodes, these electrodes can be
arranged in a kinematically defined manner so as to rest on a step
in each instance and can subsequently be fixed by material bonding
as was already mentioned. In this way, a defined axially symmetric
arrangement of the individual electrodes of an electrostatic
deflection system can be achieved and also permanently maintained.
The corners of individual steps of the stair structure of support
areas can be constructed as 90-degree V-grooves.
Also, a certain curvature of the individual electrodes cannot be
avoided for reasons relating to manufacturing technique,
particularly in that the rod-shaped electrodes which can be used in
a deflection system according to the invention have a high aspect
ratio, i.e., a large length compared to the outer diameter or
cross-sectional dimensions. However, when using a deflection system
according to the invention, a curvature of this kind can negatively
impact the defined forming of electrical fields for the deflection
of a corpuscular beam.
For this reason, the respective curvature of the individual
electrodes should be taken into consideration when assembling and
fixing to the carrier members. For example, the arrangement and
orientation of the individual electrodes that are fastened to the
carrier members can be advantageously selected in such a way that
their respective convex curvature is directed radially outward in
relation to the longitudinal axis of the deflection system. In this
way, a positive influence can again be exerted on the desired
axially symmetric arrangement of the electrodes at the carrier.
Further, the individual electrodes can be measured prior to
assembly to determine the respective curvature of an electrode.
In this way, electrodes having identical curvatures, but at least
curvatures lying within a close tolerance range, can be used for a
deflection system in a particularly advantageous manner.
Optical measuring methods, known per se, can be used to determine
the curvature. In order to ensure that the orientation of the
convex curvature of electrodes is also detected and can be kept
within a tolerance range of plus or minus 5.degree. in radial
direction during the mounting of the electrodes in the carrier
members, the respective rod-shaped electrodes can be ground at an
oblique angle at least at one end face. This obliquely inclined end
face can then be used to determine the orientation of the convex
curvature. After this is determined, this end face, or the opposite
end face, can be provided with a corresponding mark that can convey
information about the orientation of the curvature of the
respective rod-shaped electrode.
Accordingly, a kind of barrel-shaped or waisted cage can be formed
by means of the electrodes which are arranged and correspondingly
fixed in the carrier and oriented in a corresponding manner.
In a particularly advantageous embodiment form, at least one
additional support area can be provided and formed at the carrier
members and consequently also after assembly at the carrier. A
support area of this kind can preferably be arranged centrally
between the support areas arranged at the ends so that the
outwardly curved rod-shaped electrodes can contact this support
area arranged between the two outer support areas and the curvature
of the rod-shaped electrodes is reduced as far as possible.
This third support area and also, if necessary, another support
area can have a stepped structure, as was already mentioned, and
the positioning and fixing of the rod-shaped electrodes can
likewise be carried out analogously in the corresponding grooves of
a respective step.
The carrier members which are to be assembled to form a carrier
should be produced from a dielectric material having high strength
and dimensional stability. Further, it should be mechanically
machinable as far as possible for the desired highly precise
microstructuring. For example, glass ceramics are suitable
materials for the carrier members. In this way, for instance, as
opposed to the use of metals, eddy currents can be prevented.
In order to prevent electrostatic charges, these carrier members
should be provided with an electrically conductive coating which
can then be connected to ground when using a deflection system
according to the invention.
In the following, the invention will be described more fully by way
of example.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a top view of a carrier member showing an example of a
deflection system according to the invention;
FIG. 2 is a side view of a carrier member with electrodes; and
FIG. 3 is a side view showing two carrier members according to FIG.
1 which are connected to one another to form a common carrier.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a top view of a carrier member 1.1 which can be
assembled with another carrier member 1.2 (not shown) to form a
common carrier 1 and can then be connected to one another,
preferably in a material engagement, e.g., by laser soldering.
The support areas 3.1, 3.2 and 3.3 are formed at the two outer end
faces and centrally therebetween.
The carrier member 1.1, as well as the carrier member 1.2 not
shown, can be produced from a glass ceramic by mechanical
micromachining. In particular, the stair structure of the support
areas 3.1, 3.2 and 3.3 can be mechanically formed in this way so as
to have the desired high precision.
The carrier member 1.1 is coated with a layer system described as
follows.
In order to prevent electrostatic charges, the carrier members 1.1
and 1.2 should be provided with an electrically conductive coating
4 which can then be connected to ground when using a deflection
system. For this purpose, the outer surfaces of the carrier members
1.1 and 1.2 can be provided with a metal coating or other
electrically conductive coating 4.
An individual layer or a layer system 4.1 and 4.2 comprising metal
or metal alloys can be formed for this purpose. For example, it is
possible to provide the surface of carrier members 1.1 and 1.2 with
a base layer 4.1 of nickel that is provided with an overlayer 4.2
of gold as a layer system. A nickel coat and subsequently a gold
coat can be provided by an electroless process. The gold overlayer
4.2 provides for improved wetting for a material-bonding connection
by soldering.
However, other coating methods and layers or layer systems by which
coats with very good conductivity and good wetting behavior can be
generated and can also be used. This also protects against
environmental influences and affords the possibility of cleaning by
means of plasma. Instead of gold, other metals which likewise
possess this property can also be used.
The coating 4 between the individual surface regions at the support
areas 3.1, 3.2 and 3.3 is then removed subsequently in order to
achieve electrical isolation between the individual areas.
The regions of the support areas 3.1, 3.2 and 3.3 of the carrier
members 1.1 and 1.2 which come into contact or are capable of
coming into contact with the rod-shaped electrodes 2 may not be
electrically conductive in relation to one another; therefore, each
individual electrode 2 is held so as to be electrically insulated
from its neighbor.
These surfaces of the support areas 3.1, 3.2 and 3.3 can either not
be coated or the coating can be removed again subsequently. This
can be carried out, for example, by means of a mechanical removal
by microcutters or chemically by localized etching.
As shown in FIG. 2, the rod-shaped electrodes 2 can be produced
from dielectric materials which are coated in an electrically
conductive manner at their outer surfaces subsequently. This is
advantageous when used in rapidly changing magnetic fields.
For example, the rod-shaped electrodes 2 can be produced from a
glass, preferably by a drawing process. Borosilicate glass,
preferably silica glass, can be used for production.
When producing rod-shaped electrodes 2 of the kind described above,
care must be taken to provide as far as possible for uniform
roundness and cylindricity, to maintain a constant diameter and
prevent bending and twisting.
After manufacture, selection and sorting can be carried out
according to certain guidelines by means of suitable measuring
methods. The outer diameter and the respective bow/curvature can be
appropriate selection parameters so that the rod-shaped electrodes
2 used in a deflection system are at least almost identical.
A bow/curvature should be less than 5 .mu.m over the entire length
of an electrode 2 assuming an electrode length of 200 millimeters
for example. Deviations from roundness and cylindricity should be
less than 1 .mu.m. Variations in diameter should likewise be less
than 1 .mu.m.
In order to ensure that the orientation of a convex curvature of
electrodes 2 is also detected and can be kept within a tolerance
range of plus or minus 5.degree. in radial direction during the
mounting of the electrodes 2 in the carrier members, the respective
rod-shaped electrodes 2 can be ground at an oblique angle 2.1 at
least at one end face. This obliquely inclined end face can then be
used to determine the orientation of the convex curvature. After
this is determined, this end face, or the opposite end face, can be
provided with a corresponding mark 7 that can convey information
about the orientation of the curvature of the respective rod-shaped
electrode 2.
The rod-shaped electrodes 2 produced from the dielectric material
can then be provided subsequently with an electrically conductive
coating 4 having good electrical conductivity, high adhesive
strength, and suitability for use under vacuum. Further, they
should be solderable and free from hydrocarbons. It has turned out
that these characteristics can be achieved in a particularly
advantageous manner by a layer system comprising a plurality of
layers of different metals. A layer system of this type can be
formed by a multi-step sputtering process. However, individual
coats can also be used.
An adhesion-imparting coat of titanium can be formed directly on
the outer surface of the electrodes 2 produced from dielectric
material. A diffusion barrier layer of platinum can then be applied
to this titanium coat and a solderable gold layer can then be
applied to this platinum layer. A layer system of this kind can
have a total thickness of about 300 nm.
If possible, at least eight electrodes 2 should be used in a
deflection system according to the invention. However, for many
applications, a larger quantity of electrodes 2 is preferable. For
example, twelve or twenty such electrodes 2 can be used in a
deflection system without difficulty. However, for simple
applications four electrodes 2 may also be sufficient.
It is also advantageous to arrange electrodes 2 with different
diameters in relation to the longitudinal axis 6. The electrodes 2
can be arranged in a deflection system on at least two, preferably
at least three, different diameters in relation to the longitudinal
axis 6 of the deflection system. In an arrangement of this kind,
the axial symmetry should also be taken into account. Accordingly,
an electrical field that is as homogeneous as possible is formed in
the interior of the system and achieves particularly good
suppression of higher-order interference, e.g., third-order and
fifth-order fields. This can also be achieved by other arrangements
of electrodes 2 with identical or different diameters.
As was already mentioned, there are regions at the support areas
3.1, 3.2 and 3.3 which do not have electrically conductive coating.
For this reason, shielding flanges 5 are advantageously arranged in
the region of the support areas 3.1, 3.2 and 3.3.
For example, two shielding flanges 5 can form outer terminations at
the ends of the carrier members 1.1 and 1.2. They can be connected
by material bonding to the carrier members 1.1 and 1.2 that have
already been assembled to form a carrier 1. However, these end
terminations should be formed in such a way that there are openings
through which a corpuscular beam can be directed by the deflection
system.
When a third support area 3.3 is provided at a carrier 1 for the
deflection system, a shielding flange 5 should also be provided
there. This can be produced as an annular structure, and the outer
contour at the step contour of the support area 3.3 can be
constructed with corresponding recesses for the electrodes 2 while
taking into account the arrangement of the electrodes 2. Another
aspect of this latter feature is that the electrodes 2 are also not
exposed to forces leading to deformation and twisting.
The electrodes 2 can be connected to the carrier members 1.1 and
1.2 in particular at the support areas 3.1 and 3.2 arranged at the
end of the carrier members 1.1 and 1.2. This can be carried out by
means of a laser soldering process with suitable solders and, if
necessary, with the addition of flux.
The material-bonding connection of the electrodes 2 to the carrier
members 1.1 and 1.2 can also be carried out by gluing. UV-curable
adhesives which are suitable for use under vacuum conditions should
preferably be used for this purpose.
The electrodes 2 which are mounted and fixed at the carrier members
1.1 and 1.2 are contacted in an electrically conductive manner at
one end. This can be carried out, for example, by soldering on thin
gold wires having a diameter of about 100 .mu.m. These gold wires
can then be connected again in an electrically conducting manner to
corresponding contact surfaces of a contact board so that each
individual electrode 2 can be acted upon by a suitable voltage for
specific deflection of a corpuscular beam. However, certain
electrodes 2 can also form groups, each of which is acted upon by
the same voltage or is connected to ground.
A contact board of this kind that is provided with contact surfaces
can be arranged at an end face of the deflection system. This can
be carried out at a shielding flange or a contact board can also be
an integral component of a shielding flange 5 of this kind.
The construction of the stair structures at the support areas 3.1,
3.2 and 3.3 can be seen particularly clearly from the side view of
the carrier member 1.1 shown in FIG. 2.
An electrode 2 is inserted into every 90-degree V-groove of a step
so as to be positioned in a defined manner and, as was also already
explained in the general description, is connected by material
bonding.
Further, it is clear from FIG. 2 that electrodes 2 are arranged on
different diameters in relation to the longitudinal axis of the
carrier 1 and of the deflection system according to the invention,
and the electrodes 2 can also have different outer diameters. The
electrodes 2 arranged on a common diameter in relation to the
longitudinal axis should have the same outer diameter.
FIG. 3 shows the carrier members 1.1 and 1.2 which are assembled
and joined to form a carrier 1 and which have an electrode 2
fastened thereto in each instance. The arrangement of electrodes 2
on different diameters in relation to the longitudinal axis can
also be seen clearly in this figure.
The electrodes 2 were obtained from silica glass by a drawing
process and, as was explained in the general description, were
provided with a layer system with an adhesion layer of titanium, a
diffusion barrier layer of platinum, and a gold layer.
While the foregoing description and drawings represent the present
invention, it will be obvious to those skilled in the art that
various changes may be made therein without departing from the true
spirit and scope of the present invention.
* * * * *